Aircraft designers are constantly searching for ways of connecting components together to produce a strong bond while using a minimum of additional material to form the bond in order to keep the weight of the aircraft structure as low as possible. One proposal has been to bond components together using an adhesive and this has proved successful but requires the bond to be compressed while the adhesive sets. When the bonded region is readily accessible, the components can simply be compressed by means of a clamp applied to the bonded region; however, when the bonded region is, not accessible, for example because one of the components has an enclosed cavity above the bonded area so that clamps cannot reach the bonded area, the two components must be held in a press to urge the two components together while the adhesive sets. However, not only is it impractical to place large structures in a press but also, since pressure in the press is applied to the whole structure, the pressure can deform parts that are not being bonded and to avoid this it is often necessary to support such parts while the components are in the press. The provision of supports is time-consuming and in many cases the structure being bonded precludes the use of removable internal supports, for example when it is desired to bond two components together to form an enclosed cavity; in the latter case, the support could be built into the enclosed space but this increases the weight of the resulting structure and defeats the primary object of adhesive bonding. The setting of the adhesive can often be accelerated by heat and to achieve simultaneous heating and compression of the adhesive the structure can be placed in an autoclave; however, large autoclaves are expensive.
U.S. Pat. No. 3,879,247 describes a method of sealing packages by incorporating a magnetically susceptible strip in one flap of the package, placing a second flap over the first with a layer of adhesive between them, placing a magnetic coil against the second flap to attract the strip in the first flap and hold the two flaps together while the adhesive is setting. However, the incorporation of magnetically susceptible strips is disadvantageous, particularly in aircraft where they would add to the weight of the structure and where they could affect the working of instruments.
GB No. 586,978 describes a method of bonding articles together by placing a magnet on one side of an assembly to which adhesive has been applied and an armature on another, so that the adhesive is compressed by the magnetic attraction between the magnet and the armature while it is setting but such an arrangement does not allow the joining of components having enclosed cavities therein.